Mapping Brain-Wide Afferent Inputs of Parvalbumin-Expressing GABAergic Neurons in Barrel Cortex Reveals Local and Long-Range Circuit Motifs

Abstract

SUMMARY Parvalbumin (PV)-expressing GABAergic neurons are the largest class of inhibitory neocortical cells. We visualize brain-wide, monosynaptic inputs to PV neurons in mouse barrel cortex. We develop intersectional rabies virus tracing to specifically target GABAergic PV cells and exclude a small fraction of excitatory PV cells from our starter population. Local inputs are mainly from layer (L) IV and excitatory cells. A small number of inhibitory inputs originate from LI neurons, which connect to LII/III PV neurons. Long-range inputs originate mainly from other sensory cortices and the thalamus. In visual cortex, most transsynaptically labeled neurons are located in LIV, which contains a molecularly mixed population of projection neurons with putative functional similarity to LIII neurons. This study expands our knowledge of the brain-wide circuits in which PV neurons are embedded and introduces intersectional rabies virus tracing as an applicable tool to dissect the circuitry of more clearly defined cell types.

Lateralized decrease of parvalbumin+cells in the somatosensory cortex of ASD models is correlated with unilateral tactile hypersensitivity

“…In particular axons of PV cells in layers 2/3 and 5/6 extend through several columns, in addition to their local and translaminar innervation (Atallah BV et al 2012;Tremblay R et al 2016). As reported by other groups (Hafner G et al 2019), PV + cells were not detected in layer I of the somatosensory cortex in any of the animals. In our samples from ASD and WT groups, PV + cells were present in layers II-IV and V-VI ( Figs.…”

Spatiotemporal refinement of signal flow through association cortex during learning

“…Future studies may investigate whether in tasks distinct from ours, where spatial aspects are important, posterior association areas show enhanced activity whereas anterior areas including RL may be suppressed. Such suppression could be mediated through long-range inputs targeting inhibitory cell types [54][55][56] or long-range GABAergic projections originating from subcortical areas such as the hippocampus [57][58][59] . Alternatively, RL could be the association area for processing tactile information whereas PM is responsible for visual information and not needed in our task.…”

Circuits in the absence of cortical layers: increased callosal connectivity in reeler mice revealed by brain-wide input mapping of VIP neurons in barrel cortex

“…Repetitive single-whisker C2 stimulation elicited hemodynamic responses, which appeared similar among WT and reeler mice (Figure S2A, C). The overlay of the signal with the blood vessel pattern on the cortical surface (Figure S2B, D) provided a map to accurately target the whisker-related cortical module with an injection (Hafner et al, 2019). As a proof of principle, we injected AAV-TVA 66T -EGFP-oG and RV-mCherry centered on C2 in a WT animal and sectioned the cortex tangentially.…”

“…The injection pipette was inserted at this location in WT and reeler animals. The surgery was performed as in (Hafner et al, 2019).…”

“…This procedure was performed as described earlier (Guy et al, 2015; Hafner et al, 2019). Briefly, Whisker C2 on the left muzzle was stimulated with a piezo actuator at 5Hz.…”